Intervertebral spacer implants, either alone or further provided as an assembly, inclusive of a retention mechanism to help alleviate expulsion and movement of the implant when placed in the spine, are well known. Such implant assemblies are advantageous in providing an implant that is easier to insert in the spine, and which resists expulsion subsequent to implantation. Intervertebral spacer implant assemblies which include a spacer and a plate, where the plate comprises a supplemental or alternative retention mechanism having one or more holes in the anterior end of the plate that are directed toward the superior, inferior or both endplates of adjacent vertebrae are also known in the art. Such implants are used to stabilize and immobilize the spinal segments in the treatment of single or multi-level degenerative disc disease, spinal stenosis, and failed previous fusions, as well as other spine conditions.
The problem with many of these implants resides in preservation of the highest degree of mobility possible, while avoiding backing out or loosening of the implant assembly fastening elements, such as bone screws and the like.
As will be illustrated herein, the prior art devices often lack sufficient means to insure lockable engagement of the anterior instrumentation and fastener elements, nor do they provide passive means to enable screw retention. In many instances the screw retainer components are provided as separate elements, which must be installed by the surgeon via a separate and distinct step subsequent to application of the fixation element.
An additional deficiency of the prior art devices is that they are not designed to enable the surgeon to place multiple bone fasteners within a single entry point, so as to provide the surgeon with the freedom to moderate the angularity of the fastener elements in such a manner that they can be targeted for both the superior and inferior vertebral bodies surrounding the implant.
The instant invention satisfies a long felt need in the art by providing a biomechanical implant with stabilizing instrumentation, (which instrumentation will alternatively be referred to as anterior, posterior or lateral instrumentation throughout the present disclosure) which provides stabilization to the adjacent vertebra wherein a single opening in such instrumentation permits bone screws or equivalent fixation elements to be positioned within both the superior and inferior vertebral body surrounding the implant, and wherein said bone screws or equivalent fixation elements are constructed and arranged to cooperate with an elongated and dished curvilinear opening formed within a first surface of the anterior instrumentation, effective to urge the fixation elements into locking engagement, one to the other, as well as with the anterior instrumentation, upon final fixation of the components, thereby forming a frictionally engaged assemblage. A further long felt need is met by the inclusion of a screw retainer component, which is in the form of a passive locking ring or equivalent device, which constitutes a third piece of instrumentation in this device. The screw retainer component resides in a mounting area formed near the first surface of the anterior instrumentation and is constructed and arranged to deflect from a resting position, so as to allow passage of each fastener element, subsequent to which passage, the screw retainer component returns to its initial position so as to block any of the fasteners from separating from the anterior instrumentation, should loosening or breakage occur.